1. Field of the Invention
The present invention relates to a wireless IC device for a radio frequency identification (RFID) system which enables non-contact data communication via electromagnetic waves.
2. Description of the Related Art
Recently, RFID systems have been used as article management systems. For information transmission, an RFID system enables non-contact communication between a reader/writer that generates an induction field and a wireless IC device that is attached to an article and stores predetermined information.
FIG. 1 is an external perspective view illustrating an example of a metal article to which an IC tag label described in Japanese Unexamined Patent Application Publication No. 2003-6599 is attached.
An IC tag label 102 has a rectangular thin film shape. The IC tag 102 has an IC chip 102a at the center thereof and a thin-film antenna 102b in an outer region thereof. To accommodate the IC tag 102 in a floating state in a recessed portion 105a in a head 101a of a metal article 101, the IC tag 102 is secured to the bottom surface of a non-metallic plate 103. The non-metallic plate 103 is disposed in the recessed portion 105a and secured therein. The head 101a has a notch 106.
With the configuration described above, a magnetic field generated by the antenna 102b in the IC tag 102 can be formed into a loop that passes through the notch 106, the exterior of the metal article 101, and the non-metallic plate 103 and returns to the antenna 102b. 
A metal article with an IC tag is thus produced.
However, the IC tag and the metal article provided with the IC tag described in Japanese Unexamined Patent Application Publication No. 2003-6599 have the following problems.
(1) Forming a complex structure including the recessed portion and the notch involves a long process and the use of additional components. This leads to an increase in the cost of manufacturing the metal article.
(2) Producing the non-metallic plate to cover the recessed portion involves the preparation of a material that is different from that of the metal article, a long process, and the use of additional material. This leads to an increase in the cost of manufacturing a metal structure. Additionally, application distortion occurs at a portion in which the non-metallic plate is secured to the metal article, due to a difference in thermal expansion coefficients. This may cause cracks or fractures.
(3) Forming an antenna pattern is required to enable the IC tag to operate.